Water processing dates back to ancient civilizations, where purification methods such as charcoal filtering, sunlight exposure, boiling, and straining were applied for purposes of improving taste and clarity of water. The 1800s saw the rise of water facilities capable of providing water to entire towns. Simultaneously, scientists and epidemiologists elucidated how microscopic organisms could transmit disease through water, and, as a result, most drinking water treatment systems employed a number of filters, e.g. containing sand and/or charcoal, to reduce turbidity and bacteria population. The early 1900s marked the birth of modern treatment facilities which utilized chlorine and ozone disinfectants for increased ability to eradicate pathogens. Although technological improvements and increased federal regulations reduced the prevalence of pathogens, it became evident in the 1960s that industrial and agricultural chemicals posed additional public health concerns. Water treatment facilities implemented new purification techniques to address these contaminants.
Despite modern advances in waterborne disease prevention, severe outbreaks still occur in the U.S. and other developed nations of the world. The 1993 outbreak of Cryptosporidium in Milwaukee, Wis., the largest documented waterborne disease outbreak, demonstrated to public health officials that not all waterborne pathogens could be eliminated using established disinfection techniques. Similar outbreaks of E. coli in Canada and cases of Cryptosporidium outbreaks in the U.K. and Europe point to a serious concern for public health. Furthermore, waterborne pathogens resistant to current purification methods continue to emerge.
To improve uniformity of water treatment facilities across the nation, the U.S. Congress enacted the Safe Water Drinking Act (SWDA) in 1974 to set standards for monitoring and treatment techniques and maximum contamination levels. An essential part of the SWDA and its amendments in 1986 and 1996 was to establish routine monitoring of the nation's water supply to guarantee that chemical toxins and pathogens are maintained at levels that minimize health risk. Currently, quantitative analysis of chemical and biological pollutants is performed with analytical methods such as gas chromatography coupled to mass spectrometry (GC-MS). See, for example, “Standard Methods for the Examination of Water and Wastewater,” by American Public Health Association, American Water Works Association, and Water Environment Federation (20th ed. Washington, D.C., 1998), incorporated herein by reference. Tables 1A-1D below shows the quantity of contaminants under regulation and their categorization by the Environmental Protection Agency. Additionally, summaries of the testing frequency, the cost per analysis, and the analytical method are provided.
TABLE 1AEPA Contaminant CategoryTotal Tests in CategoryMicroorganisms4Disinfection Byproducts11Disinfectants3Inorganic Chemicals16Organic Chemicals53
TABLE 1BRequired Testing FrequencyAnalytes TestedBi-annually1Quarterly65Monthly1Daily2Continuously2Depends on Source3Information Unavailable4
TABLE 1CAnalytes TestedCosts per Analysis(%)$200-$40065 $50-$2006Under $503
TABLE 1DAnalytesTestedAnalytical Method(%)Gas Chromatography w/Mass Spectrometry42Gas Chromatography w/Electron Capture Detection24Gas Chromatography w/Photoionization Detection24Inductively Coupled Plasma w/Mass Spectrometry11Graphite Furnace Atomic Absorption10Colorimetry6Inductively Coupled Plasma w/Atomic Emission6SpectrometryHigh Performance Liquid Chromatography with5Ultraviolet DetectionDPD Ferrous Titrimetric3Gas Chromatography w/Nitrogen-Phosphorus Detection3High Performance Chromatography w/Post-Column3Derivitization and Fluorescence DetectionIon Chromatography3Iodometric Electrode3Gas Chromatography with Electrolytic Conductivity2DetectionIon Chromatography w/Conductivity Detector2Cold Vapor Atomic Absorption1Enzyme Substrate Test1Gas Chromatography w/Flame Ionization Detection1High Performance Liquid Chromatography w/UV1Absorption & Fluorescence DetectorsLiquid/Solid Extraction (LSE)1Membrane Filtration1Multiple-tube Fermentation Technique1Transmission Electron Microscopy1
Analytical laboratories provide many testing services using various technologies. For example, one laboratory in the Greater Boston area offers the following tests: (Bold italics indicate tests specifically for drinking water):
  Trace MetalsInductively CoupledPlasma Spectrophotometers Cold Vapor AtomicAbsorption Spectrophoto-meter (mercury analysisonlyWet Chemistry Analysis - Oxygen demand,Bench chemistryorganic carbon, acidity, alkalinity,testsbromide, CO2, chloride, cyanide, iron, fluoride, formaldehyde, hexavalent chromium, hydrazine, nitrogen,orthophosphate, oxidizers, peroxide,phenol, phosphorus, sulfate, sulfide,fulfite, tannin & lignin, organic matter,hydrocarbons, chlorine, anions, etc.  Volatile organics-aromatics,GC/MShalocarbons, all w/various EPAGC w/various othermethods listeddetectorsExtractable organics-  other things not specifically fordrinking waterPetroleum HydrocarbonsGC  Dissolved gasses-ethane, ethane,GC-MSmethane
Known microbiological and other analytical processes are typically both time- and labor-consuming, often requiring sensitive detectors and highly trained personnel. As a result, as shown above, tests are typically performed periodically with the majority of contaminants being tested on a quarterly basis. Furthermore, many conventional methods look for a particular contaminant instead of providing a trigger that indicates that something has changed in the water composition.
Accordingly, despite improvements in analytical techniques over the past several decades, a monitoring system that is robust, low-cost, automated, and able to either detect a change in water composition or identify a wide variety of low concentration analytes in real-time is still desirable. In that regard, particularly desirable are inexpensive and highly sensitive first alert systems that continuously monitor the water supply and generate an alarm to warn of a possible water quality problem.